A&P Lecture 1.9: Peroxisomes and Proteasomes

This is an in depth  explanation of Peroxisomes and Proteasomes as a part of the cell. This lecture note is linked to A&P Lecture 1: The Cell

ANATOMY AND PHYSIOLOGY LECTURE 1.9

PEROXISOMES AND PROTEASOMES

Peroxisomes are membrane-enclosed organelles containing several specific enzymes that promote oxidative reactions. Although peroxisomes are present in most cells, they are particularly large and active in the liver.

All peroxisomes contain one or more enzymes that promote reactions in which hydrogen is removed from particular organic molecules and transferred to molecular oxygen (O 2 ), thereby oxidizing the molecule and forming hydrogen peroxide (H 2 O 2 ) in the process. The oxidation of toxic molecules by peroxisomes in this way is an important function of liver and kidney cells. For example, much of the alcohol ingested in alcoholic drinks is oxidized into acetaldehyde by liver peroxisomes.

The enzyme catalase within the peroxisomes prevents the excessive accumulation of hydrogen peroxide by catalyzing

Proteasomes  consist of large protein complexes, including several enzymes that break down and recycle proteins within the cell. Proteasomes are not surrounded by membranes. They are tunnel-like structures, similar to channel protein complexes; the inner surfaces of the tunnel have enzymatic regions that break down
proteins. Smaller protein subunits close the ends of the tunnel and regulate which proteins are taken into it for digestion.the reaction 2H 2 O 2 → 2 H 2 O + O 2 . Catalase is one of the fastest acting enzymes known (see chapter 4), and it is this reaction that produces the characteristic fizzing when hydrogen peroxide
is poured on a wound.